U.S. Pat. No. 4,828,184 describes a method for manufacturing nozzles in the form of orifice plates, which represent the so-called "S-type plates." What is meant by this term is that the inlet and outlet orifices in the orifice plate are offset from one another, forcing the flow of a fluid passing through the orifice plate to traverse an "S course." The orifice plates are formed by two planar silicon wafers that have been bonded, with a plurality of inlet orifices being provided in the upper, first silicon wafer and exactly one outlet orifice being provided in the lower, second silicon wafer fixedly connected to the first silicon wafer. The silicon wafers include areas of reduced thickness, so shearing gaps are formed between the orifices of the first wafer and the one orifice of the second wafer, parallel to the end faces of the wafers. The inlet and outlet orifices are created with a conventional masking technique involving etching on silicon wafers that have a plurality of orifice-plate structures. The truncated-pyramid contours for the orifices in the orifice plate result logically from the anisotropic etching technique.
U.S. Pat. No. 5,383,597 describes an orifice plate having an S-type plate construction and preferably produced from silicon. Regardless of the material used and the method of manufacture of the orifice plate, the orifice plate includes two fixedly-connected wafers that rest directly against one another and are flowed through one behind the other. The upper, first wafer is provided with a plurality of inlet orifices that open through into channel regions cut into the downstream end face of the first wafer. The lower, second wafer has a plurality of outlet orifices that extend from channel regions representing depressions at the upstream end face of the second wafer. In the assembled state of the orifice plate, the two wafers rest with one on top of the other such that the channel regions of the two wafers together form channels or cavities, which are flowed through between the inlet and outlet orifices. With the use of etching as the machining method for the silicon wafers, the inlet and outlet orifices always have a truncated-pyramid shape. The channels also have wall inclinations that are predetermined for etching by the crystal lattices of the silicon.
U.S. Pat. No. 5,449,114 describes an orifice plate, which is particularly suited for fuel-injection valves and has two fixedly-connected wafers that rest closely against each other. An orifice plates have a silicon or a plurality of metals, which are embodied such that a single inlet orifice extends in the upper, first wafer and opens through into a trench, which serves as a channel, at the downstream end face of the upper, first wafer. Four outlet orifices that are offset from the upper inlet orifice are cut into the lower, second wafer. An offsetting of the lower outlet orifices with respect to the inlet orifice ensures that an "course" will be formed in the flow of a fluid, particularly a fuel, flowing through the orifices.
A disadvantage shared by all of the aforementioned silicon orifice plates is that their fracture strength may be insufficient due to the brittleness of silicon. The silicon wafers are at risk of fracturing in response to continuous stress, such as at an injection valve (engine vibrations). Mounting the silicon wafers on metallic components, such as injection valves, is complicated, because special stress-free securing means must be found, and the seal at the valve is problematic. It is not possible, for example, to weld the silicon orifice plates to the injection valve. A further disadvantage is wear (e.g., erosion) of the edges at the orifices of the silicon plates due to the frequent flow-through of a fluid.
Furthermore, German Patent Application No. 483 615 describes a nozzle for fuel-injection internal combustion engines, which is likewise formed by two nozzle plates that have inlet and outlet orifices that are offset with respect to one another to generate turbulence in the flowing fuel. The two metal nozzle plates are manufactured or machined with conventional techniques (stamping, pressing, rolling, cutting, boring, milling, grinding, etc.).
A common feature of all of the conventional orifice plates is that the diverse, separately manufactured and machined nozzle plates must be connected with joining methods. This is effected, for example, through bonding for silicon wafers and welding or soldering for metallic wafers. Other work processes, such as centering the individual nozzle plates with respect to one another, are required in addition to the actual connecting methods. A possible disadvantage of these time- and cost-intensive method steps is deformities of the nozzle plates.